Help - learning about windows servers

Windows Server 2003 Enterprise is a successor of Windows 2000 Advanced Server. Is that true?
Windows Server 2003 has a similar architecture like Windows Server 2000. Is that true?
If I want to isolate some users, but I want the possibility that those users can log in (directory LocalUser), I have to create a new subdirectory called... Public? Or?
If I install / configure some services like DNS or WINS server, is there a possibility that those new configured services can have a higher priority than DHCP?

Windows Server 2003 is the successor to Win2k. BUT, Windows Server 2003 is old technology now. There are architectural differences between almost all Windows operating systems. You may find it difficult to find Windows 2003 device drives for new devices.

If you are deploying a new server you should at a minimum consider Windows Server 2008 R2 and preferably Windows Server 2012.

Don't use WINS. Its antiquated and fraught with problems. Use only DNS (Domain Naming Service) and DHCP. DHCP does not have a "higher" or "lower" priority than DNS. They are separate technologies for different purposes, but they do work together. DHCP dynamically assigns an IP address to a given device, DNS is a database of host names and IP addresses that devices refer to to quickly find resources on the network or over the Internet. DNS can (and generally should) be configured to push out the IP addresses of the DNS servers to DHCP clients.

While we can probably try and answer some of your questions, this forum isn't very good for trying learn something from the ground up. Based on your questions, I'm also thinking your a bit over your head. That's not a criticism, I understand you are probably between a rock and a hard place on some project you are tasked with that has very little budget. I suggest that you look into one of Mark Minasi's Windows Server books. Google searches may yield some good tutorials on how to set up things for your environment.

I'm going to ask the dumb question, although no question is dumb. Given this scenario, what would you do?

I have a business friend who's thinking about expanding his "network" to allow several users to run programs that are setup to allow multiple users to enter data. I did some homework with the program software company and they can do this. However, he will need to build/buy a server, buy licensing softare to run it (i.e.Windows Server), client software...etc. The program software company also has a "cloud" service to accomplish the same thing with bank level encryption, which will include updates, maintenance, backups, etc.

My feeling is to suggest the cloud because of costs encumbrancing the maintenance of the server. I'm not going to be installing the server if he chooses that, I'm just getting information for him because I know enough to be dangerous. Really, I can ask the right questions to experts.

Is this mission critical data? Is the company willing to commit mission critical data to the cloud? Is remote access required to the application and data?

IMO, if the company does not have a problem with committing the data to be stored in the cloud then they should go for it. Avoiding the initial capital costs for hardware and software licenses plus the ongoing maintenance costs should be a compelling argument for a company these days.